ARTICULATIONS OF THE VERTEBRJE. 241 



The articulating surfaces of the oblique process of the atlas 

 and vertebra dentata on each side, are invested by a synovial 

 membrane. There are, also, additional ligaments placed 

 before and behind these processes, that have an effect on their 

 motions. 



The uses of these different ligaments are very obvious when they are dissected. 

 The transverse ligament of the atlas, with the synovial membranes form an 

 articulation for the tooth-like process, which is of a peculiar kind. The liga- 

 ments that pass from this process, to the bones of the condyles of the occipital 

 bone, must have an effect in restraining the rotation of the head and atlas on 

 this process, and therefore have been called moderator ligaments. 



The Articulations of the Vertebrae with each other. 



To acquire a perfect idea of the construction of the Spine it is necessary to 

 examine, at least, two preparations of it : in one of which the bodies of the 

 vertebrse should be sawed off from the processes, so that the spinal canal may 

 be laid open. 



The bodies of all the vertebrae, except the atlas, are connected 

 to each other by the intervertebrdl fibre-cartilaginous matter 

 described in page 138, which unites them very firmly, at the 

 same time that it allows of some motion, in consequence of its 

 elasticity and compressibility. This connexion is strengthened 

 by two ligaments, which extend the whole length of the spine, 

 from the second cervical vertebra to the sacrum. 



The first of these, denominated the anterior vertebral 

 ligaments , covers a considerable part of the anterior sur- 

 face of the bodies of the vertebrae ; it is thickest in the middle, 

 and varies in its breadth in different parts of the verte- 

 bral column ; it adheres very firmly to the intervertebral 

 substance, and not so firmly to the bodies of the vertebrae. 

 It has the shining silver-like appearance of tendon, and seems 

 to consist entirely of longitudinal fibres. There are many 

 fibres which appear to be connected with it, that do not extend 

 the whole length of the spine. 



On the posterior surface of the bodies of the vertebrae, in the 

 cavity which contains the spinal marrow, is the posterior or 

 internal vertebral ligament, which, like the anterior, extends 

 from the upper part of the spine to the sacrum. 



In its progress downwards it is broader where it is in contact 

 21 



